Copper Flashings - A Manual - 1925 - Page 54

At all changes of direction or of the planes of roofs, such as where the roof of a dormer meets the main roof or the bottom of a built-in gutter turns up to meet the sides, special precaution must be taken to avoid breaks and cracks. Where copper sheets are confined in sharp angles there is a restraint of free movement and the copper warps and buckles. The sheet loses its ductility and in time fracture results. In fact a sharp bend in copper sheets is as bad as nailing for it stops the free "flowing" of the sheet and provides a place for a buckle to start.

This can be done away with by using small triangular blocks in corners and working the sheet over them in a gradual or easement curve.

Such construction makes it difficult for the roofer to make up the seams, for where the sheet is bent at an angle of less than 90 degrees it is necessary to notch out the seam, with the result that there is not a full seam with four thicknesses of copper (for flat seam construction) at the bend where the notch is made. This is not serious and can be overcome by careful soldering.

If the triangular blocks are not used, great care must be taken to avoid a crease in the copper at the bend. If the sheet is folded over on itself and then opened up — that is, if it is bent more than 90 degrees — a crease will form, which acts, under temperature change, as a hinge and ultimately cracks.

DRIPS, EDGE-, AND EAVE-STRIPS

At the outer edge of cornices and similar projections it is good practice to secure the flashings as illustrated in Figs. 12, 17, 18, etc., by means of edge-strips or drips. The two terms are used interchangeably to describe either the methods there shown or those in Fig. 82.

Fig. 82. Drips.

Drips. A drip, when not formed by an edge-strip consists of a piece of copper (at least 18-ounce, preferably 24-ounce), nailed to the top of the sheathing or to the face of the molding locked to the flashing sheet as shown. It acts both as a fastening and a drip and is satisfactory for all purposes for which the heavier edge-strip need not be used.

Edge-Strips. An edge-strip consists of a piece of brass about ⅛ of an inch thick by 1¼ inches wide screwed to the supporting face by brass screws and placed so that the sheet can be hooked under it about ⅜ of an inch to form a lock. In most instances it is placed so as to project slightly below the sheathing or the upper fillet of the molding to form a drip. This form of construction is used where a stiff fastening and a straight true edge is needed. This type of edge-strip is used with large molded gutters and cornices of copper to provide the necessary strength and stiffness to the outer edge.

Eaves-Strips. When eaves and roof edges are finished with an ornamental molding which requires protection against water from the roof an eave-strip is sometimes used. It is made as described in paragraph 53, page 36, of the specifications.

CAULKING

The materials used for caulking joints around pipes and reglets in masonry work are elastic cement, sulphur and lead. The last named is the most satisfactory in every respect. It completely fills the space, holds the copper, does not disintegrate, adjusts itself to temperature changes.

On perpendicular surfaces, etc., where the pouring of molten lead is difficult, lead wool is used. It must be well caulked, and the joint completely filled. Molten lead should also be well caulked to insure a solidly-filled joint.

After caulking the reglets are sometimes smoothed and made flush with the adjoining masonry by filling them with elastic cement. This gives a neat appearance to the finished work.

EXPANSION AND CONTRACTION

The confusion that seems to exist regarding the expansion and contraction of copper — or, for that matter, any similar live metal — has brought about an unfavorable attitude in the minds of many people.

While no attempt is here made to belittle the importance of this feature of copper work the majority of failures attributed to expansion and contraction are actually the result of improper installation and failure to observe Rule I (page 50).